Prior art high frequency cavity resonators have been manufactured inside semiconductor materials by micromachining a cavity and then plating the bottom and sidewalls. The cavity is then either left void or filled with dielectric and sometimes with ferroelectric materials before it is covered with a top metal or sandwiched with a second semiconductor plate. To electromagnetically couple to the cavity, combinations of microstrip and slots may be used. Examples of high frequency cavity resonators are disclosed in U.S. Pat. Nos. 5,821,836, 6,362,706, 6,411,182 and 7,570,137, which are herein incorporated by reference.
The use of high conductivity metals everywhere around the cavity may provide a very high Q (quality) factor. However, the cost associated with micromachining to create such high frequency cavity resonators can make this technique undesirable.
One application for a high frequency cavity resonator is an oscillator. Oscillators may use a resonator with two coupled ports for cascaded loop networks.